Electronic devices of the same function and type are often sold in different speed grades (e.g., able to function at different clock frequencies). Some such devices may have multiple integrated circuit (IC) dice of the same type and function stacked in a package. These IC dice of the same type may have been based on the same design specification, but due to manufacturing variability, the dice may have different maximum attainable operating clock frequencies (or clock speed ratings).
In order to maintain the proper setup and hold times between the IC dice in the package, the differences in speed between the IC dice chosen for the package must not be too great. Thus, the manufactured IC dice may be sorted into groups in which each group has IC dice having speeds that are within a suitable range for each group. The groups are sometimes referred to as bins. The IC dice in a bin may have many different speeds, though all fall within a designated range of speeds for that bin. Each device or package may be constructed using multiple dice from a particular bin. The packages built from the IC dice of one bin may have a different speed grade than the speed grade of packages built from the IC dice of another bin.
The range of speeds of IC dice in a bin may permit use of any of the IC dice from the bin in constructing a package without jeopardizing proper setup and hold times. However, in order to meet power ratings for the packages, some ratio of slow IC dice (dice having lower clock speed ratings) to fast IC dice (dice having higher clock speed ratings) from a bin may be used in each package. For example, a package may be constructed with three slower IC dice and one faster IC die from a bin. However, the ratio of slower IC dice to faster IC dice in the bin may not be commensurate with the desired ratio for the packages. If there are too many fast dice and too few slow dice, then some fast dice may be scrapped, resulting in increased manufacturing costs.